Apparatus and method for casting metal



3 Sheets-Sheet 1 1N VENTOR July 1, 1958 R. E. GAFFNEY APPARATUS ANDMETHOD FOR CASTING METAL Filed nec. 9, 195s R. E. GAFFNEY APPARATUS ANDMETHOD FOR CASTING METAL July 1, 1958 3 Sheets-Sheet 2 Filed DSG. 9,1955 fNm HH mY w mE o Wm n 1 M A G V LnI July 1, 1958 R. E. GAFFNEY2,840,871

APPARATUS AND METHOD FOR CASTING METAL Filed Deo. 9. 1955 3 sheets-sheetINVENT OR RICHARD E. GAFFNEY ATTORNEY United States Pater fie 2,840,871atented July l, 1958 APPARATUS AND METHOD FOR CASTING METAL ApplicationDecember 9, 1955, Serial No. 552,625

18 Claims. (Cl. 22--79) This invention relates to the handling of moltenmetal prior to the casting thereof. More particularly, this inventionrelates'to a molten metal handling method and system for transfer ofmolten metal from the source thereof, e. g. furnace or other moltenmetal holding receptacle, to a mold and which is effective ineliminating or substantially reducing the presence of foreign materialin the molten metal supplied to the mold and reducing the gas contentthereof.

In the casting of metals, e. g. aluminum and aluminum alloys, it iscommon practice to provide a body of molten metal in a suitable holdingreceptacle, e. g. oil, gas, coal or coke tired open hearth orreverberatory furnace, electrical resistance heated furnace or inductionheated furnace, The molten metal is generally fluxed in the holdingreceptacle and then transferred from the holding receptacle to thecasting station. While in some instances the relative positions of thecasting station and furnace may be such as to permit the molten metal toflow directly from the furnace into the casting station, it is common tofind the furnace spaced a given distance away from the Vcasting stationand use made ofl transfer troughs for conveying the molten metal to thecasting station. The mol` ten metal may pass from the furnace throughsuitable means such as a short transfer trough and an underpour outletinto a long transfer trough, through the long trough, down through anunderpour outlet and into the casting mold.

Such practice possesses certain inherent disadvantages with regard tothe presence of inclusions and porosity in the ultimate cast body. Inconventional practice, there is an appreciable quantity of particulatematerial in the molten metal from the furnace such as particles ofrefractory material from the furnace linings and dross particles whichpass into the casting mold and result in inr clusions in the casting.

' Further, as the metal begins pouring out of the underpour outletfeeding molten metal into the long transfer trough, the metal will fallthrough the air until the liquid level in the long trough rises to alevel sufficiently high to cover the lower end of the underpour outlet.During this period there is a tendency for entrapment of gases andmoisture in the molten metal, This results in porosity in the ultimatecasting. In addition, falling and splashing of the molten metal resultsin the formation of oxide particles which become inclusions in thecasting. Further in the casting of aluminum and aluminum alloy ingots,generally, a continuous or semi-continuous casting method is employedsuch as that disclosed in Ennor Patent No. 2,301,027. vSuch apparatusgenerally comprises a short mold shell open at the t-op and bottom, 6

suitable cooling means, and a vertically movable mold bottom. At thebeginning of the casting operation the mold bottom is at its highestelevation wherein it closes the open bottom of the mold shell to form areceptacle for themolten metal. As the molten metal solidiiies the-moldbottom is lowered continuously withdrawing the embryo ingot from thebottom of the mold shell while molten metal enters through the open topof the mold shell. Generally that portion of the embryo ingot which isjust leaving the mold shell has a molten center and a solidified portionabout the outer periphery. In practice generally two or more castingapparatuses are in close proximity to each other and common loweringmeans is employed for all mold .bottoms of such apparatuses. Accordinglythese mold bottoms are lowered s'imultaneously and it is essential thatthe molten metal from the transfer trough ow into each moldsimultaneously in order to have suicient molten metal in each mold tostart an ingot. Where a mold receives insuicient metal the outletfeeding the mold must be closed off to prevent escape of molten metal.This results in substantial loss of production and time. In conventionalpractice valve type flow regulators are employed to prevent ow of metalfrom the trough into the mold prior to the start of the castingoperation. While such devices may be satisfactory for controlling rateof flow, it is eX- ceedingly ditlcult to start metal ow through two ormore such flow regulators simultaneously since the handles of suchdevices must be rotated manually several times before an appreciablequantity of metal vbegins to flow through.

These inherent disadvantages of the prior art practice have givenrisevto excessive production lossesthrough failure to utilize each moldof a multiple continuous casting apparatus and losses through scrappingof castings due to inclusions and porosity.

Accordingly, the primary purpose and object of this invention is toprovide an improved method and means for handling molten metal prior tocasting which eliminates or substantially reduces many of thedisadvantages of the prior art techniques.

Another object of this invention is tofprovide anovel means foreliminating or substantially reducing defects such as porosity orinclusions in cast bodies.

Another object of this invention is to provide anapparatus for handlingmolten metal prior to lcasting bodies therefrom including means for theelimination or substantial reduction of inclusions from such bodies.

Another object of this invention is to provide a molten metal handlingsystem for the elimination orsubstantial reduction of defects such asporosity or inclusions from cast light metal bodies, e. g. aluminum andaluminum alloys, by the use of suitable'screening means disposed toscreen the entire cross section of molten metal.

Another object of this invention is to provide a method and system forhandling molten metal prior to the castring thereof featuring new andimproved method and means for control of initial ow of Vmolten metal.

Gther objects and advantages of this invention will be apparent from thefollowing description thereof in conjunction with the accompanyingdrawings.

ln accordance with this invention, molten metal is transferred from asuitable holding receptacle to a cast-ing station by means of anelongated `transfer trough. havingv at least one downwardly directedunderpour outletthrough which'the molten metal is fed into the castingstation. Suitable screens are placed either across the iiow of moltenmetal or about the outlets or both in such a manner that all the moltenmetal passes through such `screens to remove foreign material therefromand the flow of molten metal passing through the outlets may becontrolled by suitable control means passing down into the outlets fromabove. Further, this invention provides anrirnprove'd method and meansfor control of the initial flow of molten metal. When the metal beginsto flow, the temperature of the screens is lower than that of the moltenmetal. The lower temperature of the -screens together with :the

Vaccordance with the invention to provide excellent control of metalflow at the start of the casting operation to reduce the tendency towardinclusions and porosity in the cast body, and to permit much easiercontrol in startlng the casting operation, particularly continuouscasting of multiple ingots wherein the occurrence of produc- -tionlosses through failure to utilize each mold of a multiple continuouscasting apparatus due to non-simultaneous pouring of molten metal intosuch multiple apparatus may be reduced.

The accompanying drawings illustrate a presently preferred embodiment ofthe screening means of this invention and a presently preferred methodof oper-ation.

Figures 1 .and lA constitute a fragmentary longitudinal elevation,partly in section, of an elongated transfer trough and molds with partsremoved for purposes of clarity showing the combination of flat andcylindrical `screening means of this invention.

`Figure 2 is a fragmentary longitudinal elevation partly in section ofthe inlet end of an elongated transfer trough with parts removed forpurposes of clarity showing the use of the basket screening means ofthis invention.

Figure 3 is a cross-sectional view of the pouring trough of Figure 1taken along the line 3--3 of Figure 1.

Figure 4 is an edgeview of a U-shaped member for supporting the flatscreens of this invention.

Figure 5 is a view of the Ueshaped member of Figure 4 along the line 5-5of Figure 4.

Figure 6 is a view at right angles to the surface of .a fiat screen ofthis invention illustrating the curvature of the ends of the screen.

Referring now more particularly to the drawings in which the samereference numerals have been applied to corresponding parts, the presentinvention' involves the use of cylindrical screens 12 and some form ofscreen preceding cylindrical screens 12 such as flat screens 9 or abasket screen 5 or both.

In general, casting operations of the type dealt with in this inventionnecessitate the transfer of molten metal from a source thereof, e. g.furnace 19, to a casting station and wherein use is made of an elongatedtransfer trough for conveying the` molten metal from the source thereofto the casting station. The primary reasons for the use of such transfertrough is because of the space difficulties encountered in attempting toplace the casting station closely adjacent the furnace tap hole suchthat themolten metal could ow directly from the place of exit from thefurnace into the casting station and because of the desirability ofplacing the casting station such that it can be supplied with moltenmetal from a plurality of furnaces. The embodiment of the apparatus ofthe inventionrshown in Figures 1 and 1A comprises a relatively shorttrough or receptacle 17 suitably attached in a sealed fashion to afurnace 19 in communication with a tap hole 18. Receptacle 17 generallycomprises a shell 22 and a suitable refractory lining 20. Additionally,cast iron or other suitable metal could be used for the receptacle. Atthe end of receptacle 17, opposite the end attached to furnace 19, is aflow regulator 24 which generally comprises an externally threadedelongated member 25 mounted'in threaded relationship within a nut member26 which is supported by a suitable member 23. On the top of member 25is a suitable turning handle 27 for moving member 25 upwardly ordownwardly. Attached to the bottom of receptacle 17 is an underpouroutlet 28 through which the molten metal passes into a long transfertrough 1. Outlet 28 is provided with a tapered or conical lower endportion such that upon movement of member 25 upward or downward withrespect to the lower end portion of outlet 28 the rate of How of metalcan be increased or decreased, respectively. In normal operation thellower end of outlet 28 is submerged in the molten metal pool containedin long transfer trough 1 except when transfer is begun.

While the use of a short transfer trough or receptacle 17 has been shownand described, it is to be distinctly un trod that other means fortransferring the molten metal from furnace 19 to long transfer trough 1may be employed. For example an underpour outlet similar to outlet 28could be suitably attached in a sealed fashion directly to furnace 19 crlong transfer trough 1 could be designed as to be attached directly in asealed fashion to taphole 18 and level pour the molten metal from thefurnace into the transfer trough 1.

Transfer trough 1 may be of conventional design with a metal shell 21containing refractory lining 3 which defines a cavity 2 through whichsaid molten metal passes from the entry end to the exit end of saidtrough.

After the molten metal has entered trough 1 it ows to the end Vfurthestremoved from the entry end and passes downwardly into casting molds 32through flow control regulators 29 which are similar to thathereinbefore described in connection with underpouring the metal intotrough 1 from furnace 19. Each flow control regulator 29 generallycomprises an externally threaded elongated member 34 mounted in threadedrelationship within a nut member 35 which is supported by and atlxed toa suitable member 36. With reference to Figure 3 it can be seen thatmember 36 includes vertical portions 37 .and a horizontal portion 38.Vertical portions 37 are of sufficient thickness to permit horizontalportion 38 to clear the upper end of cylindrical screen 12. On the topof member 34 is la suitable turning handle 39 for moving member 34upwardly or downwardly. Attached to the bottom of transfer trough 1 areunderpour outlets '4 through which the molten metal passes into molds32.

While three outlets are shown in Figure 1 it is within the scope of thisinvention to employ a greater or lesser number of outlets 4 depending onthe number of molds 32. Outlets 4 are provided with tapered or conicallower end portions such that upon movement of member 34 upward ordownward with respect to the lower end portion of outlets 4 the rate offlow of metal can be increased or decreased respectively. Since thecasting apparatus forms no part of the present invention, furtherdescription of same is deemed unnecessary. However, it is to be notedthat the invention is applicable to the handling of molten metalpreparatory to casting in any type of casting apparatus, e. g.continuous casting, semi-continuous casting, use of closed bottom mold,etc.

Cylindrical screens 12 are installed over each of the underpour outlets4 which conduct metal to the mold. In 'one embodiment of this invention,cylindrical screens 12 are supported as shown particularly in Figure 3by projecting portions 13 on the upper extremity of each outlet 4. Eachcylindrical screen 12 has an inside diameter slightly greater than theoutside diameter of its respective projecting portion 13 and thus theprojecting portion 13 lits snugly within the cylindrical screen 12whereby each screen 12 is held in place.

In the preferred practice of this invention cylindrical screens 12 .areof a sulicient height that when in position each screen 12 extends to aposition above thetop of transfer trough 1. This avoids the danger ofhaving the molten metal level rise to a point above the upper edge ofcylindrical screens V12 whereby a portion of the metal llows over theupper edge and down into the mold without screening. Accordingly, allthe molten metal passing through trough 1 must pass through cylindricalscreens 12. Cylindrical screens 12 are fabricated from suitablescreening material such as black iron, stainless steel,

glass, etc. An example` of a screen wire size and, mesh which been foundto perform satisfactorily is a l2 mesh cylindrical screen fabricatedfrom .035 diameter wire.

Spaced along the length of trough 1 is at least one and preferably twoor more flat screens 9 which are disposed across the entirecross-section of cavity 2 transverse to the longitudinal axis thereofand inclined away from the entry end of trough 1. Flat screens 9 may besupported by suitable members 10 illustrated in Figures 4 and 5 whichare embedded in the refractory lining 3 of transfer trough 1 and havethe configuration of cavity 2 which in the case of the trough of Figuresl through 3 is a U shape. The width of ilat screens 9 is slightlygreater than the width of cavity 2 and accordingly the refractory lining3 is hollowed out, as indicated at 11, thereby widening and deepeningthe cavity 2 for a short distance along the portions of the troughlining 3 adjacent to that side of each member 10 which contacts flatscreen 9. This permits placing each flat screen 9 in the trough in sucha manner that all the molten metal must ow through the screen. It hasbeen found that with conventional trough linings members 10 are verydesirable since without members 10 the grooves cut in the refractorymaterial 3 have their corners worn away by flow of molten metal suchthat screens 9 are no longer firmly supported. In the practice of thisinvention it is desirable for flat screens 9 to be at least double thelength required to fit within cavity 2 when supported by members 10 withboth extremities shaped to fit within cavity 2 when in contact withmember 10 as shown in Figure 6. This design makes it possible to useeach screen twice before it is thrown away or cleaned. When a cleanscreen is used one end is placed in cavity 2 as shown in Figure l. Whencasting is complete metal freezes within the openings of that end of thescreen which was in use. For the next cast the opposite or clean end isplaced in cavity 2. After the second casting operation is complete thescreen is either thrown away or cleaned for further use. Flat screens 9are fabricated from suitable screening material, preferably stainlesssteel. An example of the screen wire size and mesh which has been foundto perform satisfactorily is a l mesh flat screen fabricated from .047ldiameterwire.

In general this invention may be carried out by employing justcylindrical screens 12 and dat screens 9, as shown `in Figure 1,however, where an outlet 28 is employed for conducting metal into trough1, it may in some instances be advantageous to employ a basket screen 5positioned immediately below such an outlet as shown in Figure 2, inlien of or in addition to ilat screens 9. Basket screen 5 is fabricatedfrom suitable screening material preferably stainless steel withcylindrical side wall 7 and a ilat bottom o, the top of basket screen 5being open. An example of the screen wire size and mesh which has beenfound to perform satisfactorily is a mesh screen fabricated from .047diameter wire. Immediately below outlet 28 and resting on the bottom 6of basket screen 5 a suitable deflector such as a flat piece ofrefractory brick 8 may be provided to prevent direct flow of metal fromthe underpour outlet 28 from burning out the bottom 6 of basket screen5.

When using the screening system of this invention the screens 5, 9 and12 are heated before the furnace is tapped to a temperature lower thanthe temperature of the molten metal. Thus, as the metal contacts eachscreen there is a slight cooling effect which increases surface tensionwhereby passage of molten metal through the screens is prevented. Thescreen may then be tapped or vibrated whereby the surface tension isovercome thereby permitting the metal to ilow through the screen.

This heats the screen to the temperature of the molten metal whereby themetal continues to iiow through. If the screens are pre-heated to theVtemperature of the molten metal, this effect will not be present. On theother hand, if the screens are too cold, the metal will get slushy andplug up the openings such that tapping or vibration of the screens willnot result in the ow of molten metal therethrough. Accordingly, anintermediate temperature is necessary. In accordance with preferredpractice where the molten metal temperature ranges from 1300" F. to l400F. the screens are pre-heated such that at the time the molten metalcontacts the screen the temperature of the screen will be not less than600 F. nor more than l200 F.

The above described effect has distinct advantages for control ofinitial metal flow. For example, where a basket screen 5 is employed themetal tends to fill up the basket screen before it flows on through therest of the trough. When basket screen 5 is almost full, it may betapped or vibrated allowing the metal to flow through to the irst flatscreen 9. lf the screen was not present it would take a substantiallength of time for the molten metal to iill the entire cavity 2 of thetrough l to the point where the lower end of underpour outlet 28 iscovered. As pointed out previously, prior to the time that the metallevel rises sufficiently to cover this outlet there is a tendency forgas and moisture entrapment and entrapment of skim and dross due to thefree fall of the molten metal into the trough and undesirable turbulencecreated thereby. Such conditions increase the tendency for porosity andinclusions to be present in the ultimate casting. By use of the chillingeffect of the screens, the metal level surrounding the outlet rises muchmore rapidly, thus minimizing porosity and inclusions.

After vibrating the basket screen 5 the metal which ilows through isstopped by the lirst flat screen 9 thereby preventing the metal issuingfrom the basket from attempting to ll the entire trough cavity 2 andthus preventing the metal level from dropping to a point below the lowerend of underpour outlet 2S. Where as shown in Figure l, cylindricalscreens 12 and flat screens 9 are employed without basket screen 5, themolten metal issuing from outlet 2S is stopped by the iirst flat screen9 whereby the metal level surrounding outlet 28 rises much more rapidlythan if the entire cavity 2 had to be lled. When the pre-determinedheight of molten metal is reached, the rst at screen 9 is tapped orvibrated and the molten metal then flows through the screen to thesecond at screen 9 which stops the metal flow. The metal level is againallowed to come up to the desired level after which the second flatscreen 9 is tapped or vibrated and the metal ows through said iiatscreen. By the use of the blocking action of cylindrical screens 12 themolten metal may be allowed to lill the trough cavity 2 from end to endbefore passing through underpour outlets into the mold. When the troughis full, a greater quantity of metal will flow into the mold in a givenperiod of time than when the molten metal passes through a trough whichis not full. The greater the quantity of molten metal which flows intothe mold in a given period of time the faster the metal level in themold rises to a point above the bottom of outlets 4 thereby resulting infurther minimization of porosity and oxide inclusions in the ultimatecasting.

In addition the blocking action of cylindrical screens 12 makes itpossible to start the metal ow through all outlets 4 simultaneouslymerely by simultaneously sub- ].ecting all screens 12 to vibration as bytapping. This 1s advantageous particularly for semi-continuous andcontinuous castlng operations since it eliminates or subg this inventionpertains to the casting of two 1l by 44" 7075 aluminum alloy .proxmately10,000 lbs. of 7075 aluminum alloy were The molten metal was stirred forabout 5 minutes and sampled for spectrometric analysis. Upon receipt ofthe analysis, the alloy composition was corrected to the exact 7075alloy composition desired by adding the necessary allowing constituents.T he composition of the melt was approximately 0.13% Si, 2.55% Mg, 1.60%Cu, 5.76% Zn, 0.20% Cr, 0.28% Fe, 0.03% Ti, balance aluminum. The moltenmetal was luxed by a suitable method and means. The temperature of themetal was on the order of 1340 F. The metal was undcrpoured from thefurnace through an underpour outlet into a transfer trough containingtwo outlets. Immediately prior to the metal entering the transfer'trough two 12 mesh cylindrical screens fabricated from .035 diameterwire were heated to a temperature of approximately 800 F. and placedover each outlet in the manner shown in Figures l and 3 and describedabove. Since only two ingots were cast in this example the troughemployed had only two outlets rather than three as shown in Figure l. lnaddition two mesh at screens fabricated from .047 diameter wire and ofthe type shown in Figure 6 were heated to a temperature of 800 F. andplaced in the transfer trough as shown in Figure l. The molten metal wasthen passed into and along the transfer trough into contact with the rstflat screen. Since the temperature of the flat screen when contacted bythe molten metal was 800 F. or slightly less due to air cooling themolten metal was cooled by the screen increasing the surface tension ofthe molten metal thereby elfectively preventing the ow of molten metalthrough the screen. Passage of the molten metal from the furnace intothe transfer trough was continued to provide a molten metal pool of apre-determined height, e. g. a height sucient to cover the bottom of theunderpour outlet through u which the molten metal enters said trough.After the pre-determined height was reached, the flat screen wassubjected to vibrations by tapping to overcome the surface tensionwhereby the molten metal passed through the first flat screen toward thesecond ilat screen. As with the rst at screen the molten metal wascooled by the second flat screen by increasing surface tension, therebypreventing flow of molten metal through said second flat screen. Whenthe molten metal pool reached a predetermined height behind the secondflat screen, it was subjected Vto vibration by tapping whereby themolten metal passed therethrough toward the cylindrical screens. As withthe flat screens the cylindrical screens cooled the molten metal incontact therewith increasing the surface tension thereof therebyelectively preventing the flow of molten metal therethrough. Flow ofmolten metal from the furnace into the trough was continued to provide amolten metal pool from end to end of said trough. The control pin foreach outlet was opened prior to commencement of the pouring operation.Accordingly, when the molten metal pool had reached the pre-determinedheight and the casting operation was ready to begin, both of thecylindrical screens were simultaneously subjected to vibrations bytapping to effectively overcome the surface tension whereby molten metalsimultaneously passed through both of the cylindrical screens and downboth outlets into the twocontinuous casting molds and two ingots weremade therefrom. All metal passing through the trough and into the moldswas subjected to screening action by the two flat screens and the twocylindrical screens, to remove foreign material therefrom.

rl`he 7075 aluminum alloy ingots produced above had excellentmetallurgical properties and were satisfactory for the production ofhigh quality products by rolling, forging or extrusion operations. Theingots'wcre subjected to reilectoscope tests and evidence of inclusionsor porosity was found to be within the maximum limits set.

pertains to the casting of two 11" by 44 7075 aluminum alloy ingotshaving a length on the order of 82 inches. Approximately 10,000 lbs. of7075 aluminum alloy were charged and melted in an oil red open hearthfurnace. The molten metal was stirred for about 5 minutes and sampledfor spectrometric analysis. Upon receipt of the analysis, the alloycomposition Was corrected to the 7075 alloy composition desired byadding the necessary alloying constituents. The composition of the meltwas approximately 0.15% Si, 2.61% Mg, 1.58% Cu, 5.75% Zn, 0.20% Cr,0.33% Fe, 0.03% Ti, balance aluminum. The molten metal was fluxed by asuitable method and means. The temperature of the metal was on the orderof 1340 F. The metal was underpoured from the furnace through anunderpour outlet into a transfer trough containing two outlets.Immediately prior to the metal entering the transfer trough two 12 meshcylindrical screens fabricated from .035 diameter wire were heated to atemperature of approximately 800 F. and placed over each outlet in themanner shown in Figures 1 and 3 and described above. Since only twoingots were cast in this example the trough employed had only twooutlets rather than three as shown in Figure l. In addition two 10 meshflat screens and one basket screen fabricated from .047l diameter wirewere heated to a temperature of 800 F. and placed in the transfer troughas shown in Figures 1 and 2. The molten metal was then passed into andalong the transfer trough into contact with the basket screen. Since thetemperature of the basket screen when contacted by the molten metal was800 F. or slightly less due to air cooling the molten metal was cooledby the screen increasing the surface tension of the molten metal therebyeffectively preventing the low of molten metal through the screen.Passage of the molten metal from the furnace into the basket screen wascontinued to provide a molten metal pool of a pre-determined height, e.g. a height suflicient to cover the bottom of the underpour outletthrough which the molten metal enters said trough. After thepre-determined height was reached, the basket screen was subjected tovibrations by tapping to overcome the surface tension whereby the moltenmetal passed through the basket screen toward the first flat screen. Aswith the basket screen the molten metal was cooled by the first flatscreen by increasing surface tension thereby preventing llow of moltenmetal through said rst at screen. When the molten metal pool reached apre-determined height behind the first flat screen, it was subjected tovibration by tapping whereby the molten metal passed therethrough towardthe second lat screen. When the molten metal pool reached apre-determined height behind the second flat screen, it was subjected tovibration by tapping whereby the molten metal passed therethrough towardthe cylindrical screens. As with the flat screens the cylindricalscreens cooled the molten metal in contact therewith increasing thesurface tension thereof thereby effectively preventing the ilow ofmolten metal therethrough. Flow of molten metal from the furnace intothe trough was continued to provide a molten metal pool from end to endof said trough. The control pin for each outlet was opened prior tocommencement of the pouring operation. Accordingly, when the moltenmetal pool had reached the pre-determined height and the castingoperation was ready to begin both of the cylindrical screens weresimultaneously subjected to vibrations by tapping to effectivelyovercome the surface tension whereby molten metal simultaneously passedthrough both of the cylindrical screens and down both outlets into thetwo continuous casting molds and two ingots were made therefrom. Allmetal passing through the trough and into the molds was subjected toscreening action by the basket screen, two flat screens and the twocylindrical screens, to remove foreign materials therefrom.

The 7075 aluminum alloy ingots produced above had `9 excellentmetallurgical properties and were satisfactory for the production ofhigh quality products by rolling, forging or extrusion operations.l Theingots were subjected to reflectoscope tests Vand evidence of inclusionsor porosity was found to be within the maximum limits set by sonicstandard for V7 075 plate.

While there has been shownand described hereinabove the presentpreferred embodiments of this invention, it is to be understood that theinvention is not limited thereto and that various changes, alternationsand modifications can be made thereto without departing from the spiritand scope thereof as dened in the appended claims, wherein what isclaimed is:

1. A molten metal handling system comprising an elongated transfertrough having at least one underpour outlet in said trough, a verticallydisposed cylindrical screen in axial alignment with said outlet, saidcylindrical screen extending from a position in contact with the upperend of said outlet to a position above the top of said transfer trough.

2. The molten metal handling system of claim 1 wherein a projectingportion is provided on the upper extremity of said underpour outletwhich projecting portion iits snugly within the lower portion of saidcylindrical screen thereby supporting said screen.

3. A molten metal handling system comprising a source of molten metal, atransfer trough having a cavity through whichv said molten metal passesfrom the entry end to the exit end of said trough, means for passage rofmetal from said source to said transfer trough, said transfer troughbeing provided with at least one underpour outlet passing from thebottom of said cavity at the exit end of said trough to a position`below the bottom of said transfer trough, a vertically disposedcylindrical screen in axial alignment and in contact with said outletsaid cylindrical screen extending from the upper end of said outlet to aposition above the top of said transfer trough, and at least one flatscreen disposed ahead of said cylindrical screen and across the entirecross section of said cavity transverse to the longitudinal axis of saidtrough and inclined away from the entry end of said trough.

4. The system of claim 3 wherein a member conforming to thecross-section of said cavity is affixed in said trough to support saidflat screen and wherein the width of said Vfiat screen is slightlygreater than the width of said cavity, said cavity having a portionwhich has been .widened and deepened for a short distan-ce along theportion of said trough, adjacent the side of said member which contactssaid at screen.

5. The molten metal handling system of claim 4 wherein said flat screenis at least double the length required to fit within said cavity whensupported by said member and wherein both ends of said flat screen areshaped to fit within said cavity in `contact with said member.`

6. A molten metal handling system `comprising a suitable transfer troughthrough which molten metal passes from the entry end to the exit end ofsaid trough, said trough comprising a metal shell containing arefractory lining which defines a cavity, and at least one underpouroutlet passing from the bottom `of said cavity at the exit end of saidtrough through said refractory lining to a position below the bottom ofsaid transfer trough, a vertically disposed cylindricalV screen in axialalignment and in contact with said outlet, said Vcylindrical screenextending from the upper end of said outletto a position above the topof said transfer trough, a projecting portion being provided on theupper end of said underpour' outlet which projecting portion Vfitssnugly within the lower lportion of said cylindrical screen therebysupporting said screen, at least oneiiat screen disposed ahead of saidcylindrical screen and across Vthe entire crosssection of said cavitytransverse to the longitudinal axis of said trough and "inclined` awayfrom the entry end of said trough, a suitable member conforming to thecrosssection of said cavity embedded in said refractory lining tosupport said lat screen, the width of said flat screen being slightlygreater than the general width of said cavity, said cavity having aportion which has been widened and deepened for a short distance alongthe portion of said trough adjacent the side of said U-shaped memberwhich contacts said tlat screen.

7. The system of claim 6 wherein the screening comprising saidcylindrical screen is l2 mesh and fabricated from .035 diameter wirewhile the screening comprising said flat screen is l0 mesh andfabricated from .047 diameter wire. f

8. A molten metal handling system comprising a transfer trough throughwhich said molten metal passes from the entry end to the exit end ofsaid trough, said trough including a refractory lining defining acavity, and at least one underpour outlet in the exit end of said troughwhich outlet passes from the bottom of said cavity through saidrefractory material to a position below said transfer trough, downwardlydirected outlet means disposed above the entry end of said trough andthrough which molten metal passes into the entry end of said trough, abasket screen comprising a cylindrical side wall and a at bottom, thetop of said basket screen being open, said basket screen beingpositioned within said cavity of said trough immediately below saidoutlet means through which the molten metal enters said trough, at leastone flat screen disposed across the entire crosssection of said cavitytransverse to the longitudinal axis of said transfer trough and inclinedaway from the entry end of said trough, a cylindrical verticallydisposed screen in axial alignment and in Contact with said outlet inthe exit end of said trough, said cylindrical screen extending from theupper end of said outlet to a position above the top of said transfertrough.

V9. A molten metal handling system comprising a holding receptacle formolten metal, a suitable transfer trough having a refractory liningdeiining a :cavity through which said molten metal passes from the entryend to the exit end of said trough, downwardly directed means forfeeding molten metal from said receptacle to said trough, at least oneunderpour outlet in the exit end of said trough which outlet passesthrough the bottom of said cavity through said refractory material to aposition below said transfer trough, a basket screen comprising acylindrical side wall and a flat bottom, the top of said basket screenbeing open, said basket screen being positioned within said cavity ofsaid trough immediately below said downwardly directed means throughwhich the molten metal flows from said holding receptacle to the entryend of said trough, at least one flat screen disposed intermediatethe-basket screen and exit end of the trough and across the entirecross-section of said cavity transverse to the longitudinal axis of saidtransfer trough and inclined away from the entry end of said trough, asuitable U-shaped member embedded in said refractory lining to supportsaid fiat screen, the width of said flat screen being slightly greaterthan the width of said cavity, said cavity having a portion which hasbeen widened and deepened for a short distance along the portion of saidtrough adjacent the side of said U-shaped member which contacts saidfrat screen, said flat screen being at least double the length requiredto fit within said cavity when supported by said U-shaped member, bothends of said iiat screen being shaped to iit within said cavity incontact with said U-shaped member, a vertically disposed cylindricalscreen in axial alignment and in Contact with the upper extremity ofsaid outlet, said cylindrical screen extending from the upper end ofsaid outlet to a position above the top of said transfer trough, aprojecting portion being provided on the upper end of said underpouroutlet which projecting portion its snugly within said cylindricalscreen thereby supporting said screen.

10. The molten metal handling system of claim 9 11 wherein the screeningemployed in said basket screen is l mesh and fabricated from .047diameter wire, the screening employed in said at screen is mesh andfabricated from .047" diameter wire and the screening employed in saidcylindrical screen is 12 mesh and fabricated from .035" diameter wire. l

11. A system for handling molten metal prior to casting ingots therefromfeaturingnovel means for control of initial flow of molten metalcomprising a source of molten metal, an elongated transfer trough havinga cavity through which said molten metal passes from the entry end tothe exit end of said trough, means for passage of metal from said sourceto said transfer trough, said transfer trough being provided with atleast one underpour outlet passing from the bottom of said cavity at theexit end of said trough to a position below the bottom of ,said trough,a vertically disposed cylindrical screen in axial alignment and incontact with the upper end of said outlet, said cylindrical screenextending from the upper end of said outlet to a position above the topof said transfer trough, and at least one flat screen disposed ahead ofsaid cylindrical screen and across the e11- tire cross-section of saidcavity transverse to the longitudinal axis of said cavity and inclinedaway from the entry end of said trough, each of said screens being soconstructed and arranged that when maintained at a temperature lowerthan the temperature of the molten metal prior to passage of moltenmetal therethrough the surface tension of the molten metal is increasedby contact with each of said screens whereby passage of molten metalthrough the screen with which it is in contact is prevented until saidscreen is vibrated after which the surface tension of the molten metalis broken permitting it to flow through.

l2. In a molten metal handling system, means for control of initial owof said molten metal comprising a transfer trough through which saidmolten metal passes from the entry end to the exit end of said troughsaid trough including a refractory lining dening a cavity and at leastone underpour outlet in the exit end of said trough which outlet passesfrom the bottom of said cavity through said refractory material to aposition below the bottom of said transfer trough, downwardly directedoutlet means disposed above the entry end of said trough and throughwhich molten metal passes into the entry end of said trough, a suitablebasket screen comprising a cylindrical side wall and a tlat bottom, thetop of said basket screen being open, said basket screen beingpositioned within said cavity of said trough immediately below saidoutlet means through which the molten metal enters said trough, at leastone flat screen disposed across the entire cross-section of said cavitytransverse to the longitudinal axis of said cavity and inclined awayfrom the entry end of said trough, a cylindrical vertically disposedscreen n axial alignment and in contact with'said outlet, saidcylindrical screen extending from the upper end of said outlet to aposition above the top of said transfer trough.

13. In a method of casting metal bodies wherein a body of molten metalis provided in a holding receptacle, molten metal is passed therefrominto one end of an elongated transfer trough containing at least onedownwardly directed outlet and whereinthe molten metal passes along saidtrough to said outlet and thereafter passes downwardly through saidoutlet and into a mold, the improvement comprising passing said moltenmetal along said trough into contact with an upwardly extendingscreening surface provided within the trough and surrounding the mouthof said outlet, said screening surface being of a mesh size and at atemperature below the temperature of the molten metal such that themolten metal in contact with the screening surface is cooled to increasethe surface tension of the molten metal in contact with said screeningsurface thereby effectively preventing flow of molten metaltherethrough, continuing to pass molten metal from said receptacle intosaid trough to provide a molten metal pool from end to end of saidtrough, and thereafter subjecting the screening surface to vibration toeffectively overcome said surface tension whereby molten metal passesthrough said screening surface and down said outlet into the mold whilesimultaneously being subjected to a screening action to remove foreignmaterials therefrom.

14. A method according to claim 13 wherein said screening surface is ata temperature of from about 600 F. to 1200 F. at the moment molten metalflows into Contact therewith.

15. A method according to claim 13 wherein a plurality of metal bodiesare being cast simultaneously and wherein the screening surfaces aresimultaneously subjected to said vibration such that molten metal owsdownwardly into each respective mold at the same time and at the samerate of ow.

16. A method according to claim 13 wherein intermediate said screeningsurface and the end of said trough receiving molten metal from saidholding receptacle, al1 of the molten metal is passed through at leastone screening surface having a coarser mesh size than said firstmentioned screening surface and wherein the molten metal first passesinto contact with the second mentioned screening surface, said secondmentioned screening surface being of a mesh size and at a temperaturebelow the temperature of the molten metal in contact therewith such thatthe molten metal is cooled to increase the surface tension of the moltenmetal in contact with the screening surface thereby effectivelypreventing flow of molten metal therethrough, continuing to pass moltenmetal from said receptacle into said trough to provide a molten metalpool of predetermined height and thereafter subjecting the screeningsurface to vibration to effectively overcome said surface tensionwhereby molten metal passes through said screening surface and towardsaid iirst mentioned screening surface.

17. In a method of casting metal bodies wherein a body of molten metalis provided in a holding receptacle, molten metal is passed therefromdownwardly through an outlet into one end of an elongated transfertrough containing at least one downwardly directed outlet and whereinthe molten metal passes along said trough to said outlet and thereafterpasses downwardly through said outlet and into a mold, the improvementcomprising passing said molten metal downwardly into said transfertrough and into a screening surface extending upwardly and surroundingsaid incoming molten metal, said screening surface being of a mesh sizeand at a temperature below the temperature of the molten metal such thatthe molten metal in contact therewith is cooled to increase the surfacetension of the molten metal thereby effectively preventing flow ofmolten metal therethrough, continuing to pass molten metal into saidscreening surface until the level of molten metal is raised above thelower end of said receptacle outlet, and thereafter subjecting thescreening surface to vibration to effectively overcome said surfacetension whereby molten metal passes through said screening surface andinto said trough, passing the molten metal along said trough and intocontact with at least one further screening surface positioned such thatupon contact therewith by said molten metal the level of molten metal inthe trough is still above the lower end of said receptacle outlet, saidfurther screening surface being of a mesh size and at a temperaturebelow the temperature of the molten metal such that the molten metal incontact therewith is cooled to increase the surface tension of themolten metal in contact therewith thereby eiectively preventing flow ofmolten metal therethrough, continuing to pass molten metal into saidtroughV to increase the height of the pool of metal back of said furtherscreening surface, and thereafter subjecting said screening surface tovibration thereby overcoming said surface tension where- Iby moltenmetal 'passes'v through said screening surface and into contact with anupwardly extending screening surface provided within the trough andsurrounding the mouth of the outlet of said elongated transfer trough,said screening surface being of a mesh size and at a temperature belowthe temperature of the molten metal such that the molten metal incontact with the screening surface is cooled to increase the surfacetension of the molten metal in contact with said screening surfacethereby effectively preventing flow of molten metal therethrough,continuing to pass molten metal from said receptacle into said trough toprovide a molten metal pool from end to end of said trough, andthereafter subjecting said screening surface to vibration to effectivelyovercome said surface tension whereby molten metal passes through saidscreening surface and down said outlet into the mold whilesimultaneously being subjected to a screening action to remove foreignmaterials therefrom, the level of the molten metal pool in said troughremaining above the lower end of the holding receptacle outlet.

18. A method according to claim 17 wherein said screening surfaces areat a temperature of from about 600 F. to 1200 1?". at the moment themolten metal passes into contact therewith.

References Cited in the le of this patent UNITED STATES PATENTS HawkinsAug. 14, Yordy Jan. 7, Lowe Sept. 28, Rosenberg May 18, Konigsberg July1, Ennor June 14, Gerdts Dec. 25, Blau Oct. 25, Stovall Ian. 17, GunnApr. 11, Alexander June 19,

FOREIGN PATENTS France Mar. 25, Switzerland Dec. 15, `Germany Sept. 28,France Oct. 13, Great Britain Sept. 21,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Not2Y84Ox871 July 1a 1958 Richard E'. Gaffney It is hereby certified thaterror appears in the printed specification of thev above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 7 line 6v for f'allowng, read alloyng Signed and sealed this 31stday of January 1961o (SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting'Oficer Commissioner of Patents

